Categories of Computers and Computer Systems

1
Introduction to Computers and Programming

• Categories of Computers and Computer Systems
• Types of Software
• Structured Programming
• Object oriented Programming

2
Categories of Computers and Computer Systems
Classifying Computers

• Mainframe
• Largest computer, a powerhouse
• Massive memory
• Extremely rapid processing power
• Used for very large applications business,
  scientific, or military
• Must handle massive amounts of data, or many
  complicated processes

Contd..
3
Midrange Computers

• Less powerful, less expensive, and smaller
  than a mainframe
• Capable of supporting computing needs of
  smaller organizations
• Manages network of computers
• Can be minicomputers, used in universities,
  factories, or research laboratories
• Can also be servers, used for managing internal
  company networks, or web sites
• Optimized to support a computer network
• Enables file sharing, software sharing, resource
  sharing
• Servers provide the platform for electronic
  commerce
• May be database servers, or web servers, or
  transaction servers

4
Personal computer (PC)

• Referred to as a microcomputer
• Can be placed on desktop, or carried around
• Laptops/notebooks are portable desktops
• A workstation also fits on a desktop, but has
  more powerful mathematical and graphics
  processing abilities than a PC
• Used for scientific, engineering, and design work
  requiring more powerful graphics or computational
  abilities

5
Supercomputers

• Highly sophisticated and powerful computer
• Used for tasks requiring extremely rapid and
  complex calculations
• Typically use parallel processors
• Traditionally used in scientific and military
  work e.g., weapons research, weather forecasting
  using complex mathematical models
• Starting to be used in business for manipulation
  of vast quantities of data

6
Computing System

• Standalone
• Unitasking/Monoprogramming
• One single program in the main memory
• Multiprogramming
• Several programs from several users in the main
  memory
• Multitasking
• Several programs from one user in the main memory
• Time Sharing
• CPU time shared by several programs (Scheduling)
• Multithreading
• CPU time shared by several threads (program
  pieces)
• Centralized processing
• All processing is accomplished by one large
  central computer

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Distributed processing

• Use of multiple computers linked by a
  communication network for processing
• Client Server Computing

• Splitting processes between client computer and
  server computers
• Both are part of the network
• But, functions/processes are split
• Client point of entry, desktop, W/S, laptop
• User interacts with the client portion of the
  application
• The server provides the client with services,
  mainframe, or another desktop

• Downsizing
• Process of transferring applications from large
  computers to smaller ones

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Network computer and Peer-To-Peer Computing

• Thin client

• One form of client/server computing
• Client processing and storage requirements/capabil
  ities are minimal
• Bulk of processing done on the server
• Such thin clients with minimal memory, storage
  and processing power are called network computers
  (NC)
• No data or software is stored locally

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Peer To Peer Computing

• Another form of distributed processing
• Linking computers so that they can share
  processing tasks, data, even disk space
• Sometimes referred to as thick clients
• Individuals use less than 25 of their processing
  and storage capacity
• Grid Computing one form of peer-to-peer
  computing
• Applying the computational resources of many
  computers in the network to a single large and
  complex problem
• The grid computing software reclaims the unused
  computing cycles on desktops and harnesses them
  into a virtual supercomputer

Contd
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• Each form of computing is suitable for specific
  needs of the organization
• Peer-to-peer mainly for R D collaboration
• Network computing mainly for firms with a
  powerful centralized IT infrastructure

11
Types of Software

• A series of statements of instructions to the
  computer

• Program

• A set of programs
• A set of data structures which will be
  manipulated by the programs
• The accompanying documentation

• Software

• System Software

• A generalized programs that manage an service
  other programs and the computers resources, such
  as processor, communication links, and peripheral
  devices

• Application Software

• Programs written for specific applicatios to
  perform functions specified by the end users

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Typical software applications

• System software collection of programs to
  service other programs eg, compilers, editors, OS
  components, drivers, telecom s/w
• Real Time S/W

• Monitors, analyses and controls real world events
  as they occur
• An RT system must respond within strict time
  constraints (1 usec)
• Eg, missile control system

• Business S/W
• MIS applications
• Conventional data processing applications
• Interactive transaction processing
• Eg, sales, banking, accounting inventory

Contd.
13

• Engineering/Scientific S/W
• Automotive manufacturing
• Space labs
• CAD system simulation

• Embedded S/W
• ROM-based intelligent products with limited
  functions
• Consumer electronics
• Eg, Microwave key pad control, digital fuel
  control in automobiles, emission quality
  monitoring, dashboard displays

• PC softweare word processors, games, graphic
  database software
• AI Software Expert system (Knowledge based
  systems), pattern recognition (voice/image,
  theorem proving game playing, robotics
• Artificial Neural Networks simulates structure
  of human brain

14
System Modeling Approaches

• Decomposition is the strategy to deal with
  complex systems.
• Structured Approach decomposition using
  functions
• Process Model (DFD)
• Data Model (ERD)
• Architecture (Structure Chart)
• Object-Oriented Approach-decomposition using
  objects
• Object Model

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Pitfalls of Structured Paradigm

• Function / algorithm / Procedure Oriented
• Global Data vulnerable to corruption
• Unsuitable for large programs
• Good for moderately complex programs
• But, difficult to maintain and enhance
• No code reusability

16
Object Oriented Paradigm

• Eliminates above shortcomings
• Adds several new concepts
• New way of organizing and developing solutions
• Not tied to any particular language
• However, not all languages are suitable to
  implement OOPs concepts
• Small Talk, C, Ada, Java, Object Pascal

• Features
• Treats data as a critical element, not allowed to
  flow freely around the system
• Data elements are closely tied to the functions
  that operate on them

Contd
17

• Data protected from accidental/unintentional
  modification by other functions
• OOPs decomposes a problem into a no. of entities
  objects
• Then builds data and functions around these
  entities
• Combination of data and methods make up an object
• Objectgt Data Methods
• Data of an object can be accessed only by the
  methods associated with that object. Methods of
  one object can access methods of other objects.
• Objects communicate thro these method-calls,
  messages based on strict discipline.
• New data and methods can be easily added wherever
  necessary.

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Basic concepts

• Objects and Classes
• Objects are basic runtime entities in an
  object-oriented system
• May represent a person, place or any item that
  the system will handle
• Chosen such that they match some real-world
  entities closely
• Occupies memory and has an address customer,
  account
• Classes the entire set of data and code of an
  object can be made a user-defined-type using the
  concept of a class
• Objects are instances of their classes
• Open vectra creates an object vectra of class
  Opel

Contd..
19

• Encapsulation
• Wrapping of data and methods into a single unit
• Data is accessible only to the methods of the
  class
• This insulation of data from direct access by the
  program is called Data Hiding

• Abstraction
• Black box
• Representation of essential features without
  including the background details

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Inheritance

• Process by which objects of one class acquire the
  properties of another class
• Supports the concepts of hierarchical
  classification
• Helps in reusability
• Super-class attributes are inherited by
  subclasses
• Subclass is free to add its own attributes and
  methods